Any person whose legal right has been infringed can send a legal notice physically to the person or company infringing the legal right. In simple words, any person who has faced some legal issue can send a legal notice through an advocate.It is like a final warning to the receiver that the sender is all prepared to initiate a legal action and it is the final opportunity for the receiver to resolve the issue in hand properly.
The reason behind this is to bring it to the knowledge of the opposite party that the sender of notice is making the last effort to settle the matter in hand. Also, it gives a credibility to the story of the sender as it expressly states all the liabilities of the receiver.